The first commercially attractive cellular telephones or terminals were introduced in the market at the end of the 1980's. Since then, a lot of effort has been made in making smaller terminals, with much help from the miniaturisation of electronic components and the development of more efficient batteries. Today, numerous manufacturers offer pocket-sized terminals with a wide variety of capabilities and services, such as packet-oriented transmission and multiple radio band coverage.
In order to attract customers the terminal manufacturers have therefore taken further measures to strengthen their position in the competition, one such being to offer terminals with detachable covers or housings. If a user wishes to change the outer appearance of his communication terminal, he can simply buy a new cover of the desired kind. The old cover is preferably released by a simple grip without the aid of tools, where after the new cover can be snapped on. A detachable cover is generally a fairly simple element, essentially formed from a single piece of plastic or possibly metal. The cover may represent only the front side of the terminal, i.e. the side of the terminal carrying the user interface generally comprising a terminal display and keypad, a microphone and a loudspeaker. In such a design, the cover forms a separate part of the housing of the terminal, or optionally an auxiliary part to be attached outside the housing. Alternatively, the cover may include more than one piece, e.g. a front piece and a back piece devised to substantially enclose the terminal. The detachable covers are often provided in different colours, and also with more advanced patterns such as logos or images.
The detachable covers of the prior art mainly create an aesthetic effect, changing the visual appearance of the terminal. They do not, however, have any effect on the functions of the terminal. Other solutions for creating this aesthetic effect, without having to change the cover, have also been proposed.
EP 1079584 by Laurikka et al discloses a cover for an electronic device, such as a communication terminal, whose colour can be changed by means of a control signal. That cover is advantageously produced by using a material, which changes its colour as a result of the effect of an electric or electromagnetic control signal. Such a material is for example electronic ink, with which a conventional cover is coated. The appearance of cover can hence be controlled by a signal from the communication terminal. When a call or a text message arrives in the communication terminal, it indicates this to the user by changing the colour of the cover.
Also EP 564127 by Blonder shows an apparatus housing capable of changing colour. The housing has a transparent outer layer, covering a layer of electrically switchable light modulating material. This invention too suggests indicating e.g. a telephone ring by changing the housing colour.
Today there is a market need for a variety of radio communication terminals with different features in different price ranges. However, more different terminal varieties leads to increased costs in development, production, stock, distribution, and marketing. Furthermore, there is a constant or even increasing pace in development of new components, such as electronics, batteries, and displays, rendering the lifetime of a terminal model shorter and shorter before the next model is introduced. Today terminals are sold with different features and at different prices. Such features include e.g. touch-screen, speakerphone, special buttons etc. Normally, the only thing that can be changed for the user is the appearance of the housing, and the software controlling ring signals and displayed images.